The present invention relates to an improved detachable vehicle cap, or cover, and in particular to the type of caps used in conjunction with conventional pick-up trucks. In general there are two types of pickup caps. One type has the form of a shell having an open bottom and is usually bolted, or otherwise attached, to the top portion of the cargo space sidewalls. The other type of cap is a unitary box-like structure, resembling a building in design, usually having a closed bottom and fits partly within and partly without the cargo space. The present invention relates to the former, shell type, cap. Examples of such shell type caps are described in U.S. Pat. Nos. 3,390;913; 4,431,228, and 4,452,482.
The shell type caps to which the present invention relates usually have generally planar sidewalls and top portions, and are typically molded of fiberglass or lightweight metal. In lateral cross-section, such caps have a generally inverted U-shape. Shell type caps usually have a windowed rear, or hatch, portion to allow access to the interior of the cap and to provide rear vision for the driver. Typically, such caps have an integral front portion, usually windowed, positioned adjacent the truck cab. The caps are removeably detachable from the truck to facilitate the use of the truck for other purposes. The cap is typically removed from the truck bed by detaching the hold-down means and lifting the cap, either manually, or by other means, such as, jacks, a sufficient height to clear the cargo space sidewalls. The upraised cap is then moved, usually manually, to clear the vehicle structure. The cap may then be stored directly on the ground, on a prepared storage platform, or more normally, on planks in a storage area. The cap is normally replaced on the truck body be reversing the removal process.
The problem to which the present invention is addressed results from the processes of placing and replacing the cap on the truck body. The cap sidewalls nearer the hatch end are not held in attached alignment with the rear, or hatch, end of the cap because the hatch opening from the bottom prevents dimensional PG,3 stabilization across the bottom rear portion of the cap. For example, when the hatch is in an open position no lateral support, either inwardly or outwardly, is provided because of the hatch opening. When the hatch is in a closed position the sidewalls have no lateral support against outward movement. In the process of lifting and moving the cap to place it on, or remove it from, the truck bed, especially if such placing or removing is carried out in a manual fashion, the bottom rear portion of the sidewall is conveniently and usually gripped and used as a lifting and carrying area. The movement of the sidewalls inward or outward, or wobbling in and out, causes stresses to develop in the upper rear corners of the cap. Such stresses soon cause either a splitting of the door frame or a cracking in the upper rear portion of the cap, particularly near the junction of the upper sidewalls and the rear wall. Such cracks, or splits, not only result in the unsightly destruction of the outer cover plate or skin of the cap, but they result in structural damage to the cap and are the cause of leaks in the cap. Such cracks, or splits, are difficult to repair and even if repaired are subject to recracking, or resplitting, upon the next placement or removal of the cap from the truck bed.